docs: def katex_rendering_options(app):
      """Strip katex_options from enclosing {} and append ,"""
      options = trim(app.config.katex_options)
      # Remove surrounding {}
      if options.startswith('{') and options.endswith('}'):
          options = trim(options[1:-1])
      # If options is not empty, ensure it ends with ','
      if options and not options.endswith(','):
          options += ','
      return options